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B.L.E. · April 27, 2012, 07:41 PM

Using the 15 ft-lb of kinetic energy per grain of black powder rule of thumb, I calculate about 1150 fps at the muzzle.

I had to go to 90 grains of powder in a .45 cal rifle using 220 grain Maxi balls before the rifle would group. Only 70 grains is an awfully light load for a .54.

The ballistic coefficient for Maxi balls is better than for round balls, but only barely. To still be supersonic at 150 yards is going to take a real butt stomper of a load.

April 27, 2012, 07:41 PM	#5
B.L.E. Senior Member Join Date: December 20, 2008 Location: Somewhere on the Southern shore of Lake Travis, TX Posts: 2,603	Using the 15 ft-lb of kinetic energy per grain of black powder rule of thumb, I calculate about 1150 fps at the muzzle. I had to go to 90 grains of powder in a .45 cal rifle using 220 grain Maxi balls before the rifle would group. Only 70 grains is an awfully light load for a .54. The ballistic coefficient for Maxi balls is better than for round balls, but only barely. To still be supersonic at 150 yards is going to take a real butt stomper of a load.